The fragile X syndrome is the most common inherited form of mental retardation known. It also causes learning disabilities in carrier females and higher functioning males. It is relatively common, causing mental retardation in approximately 1 per 1000 in the general population. Significant advances in the molecular biology of the fragile site, including the sequencing of the FMR-1 gene within the last six months, are dramatically changing methods of diagnosis, genetic counseling and our understanding of the clinical spectrum of involvement from this disorder. In addition, as a larger number of patients are identified, many professionals in schools, private practice, and in institutions who are treating fragile X patients are in need of information regarding the most optimal intervention possible. We are requesting funding for an international fragile X conference which is focused on the two greatest areas of need: the advances in molecular biology and treatment issues. Expert speakers will be brought in from international centers and across the United States to 1) educate parents and professionals about recent advances, 2) provide a forum to standardize diagnosis, evaluation and counseling techniques, and 3) stimulate further research and international collaboration. These aims will be carried out in a four day conference in Snowmass, Colorado. It will take place in June 1992 because the field is changing so quickly that professionals cannot wait any longer for information to be disseminated and new standards discussed and set regarding diagnosis and treatment.